1. Field of the Invention
The present invention generally relates to video systems, and more particularly, to an asynchronous copy protection detector for use in such video systems that is capable of, among other things, detecting the presence of pseudo-synchronization pulses in video signals without utilizing horizontal and/or vertical synchronization signals.
2. Background Information
Copy protection techniques are often utilized in the video industry to prevent the production of unauthorized video copies. One such copy protection technique involves inserting pseudo-synchronization pulses on certain lines of each video field. When video information including such pulses is copied, the pulses cause synchronization problems to occur in the resultant copy. Products enabling the aforementioned type of copy protection are commercially-available from companies such as Macrovision.
In many video systems, it is necessary to detect the presence of pseudo-synchronization pulses in video signals in order to inhibit the recording process. For example, some video systems may strip such pseudo-synchronization pulses from video signals during certain signal processing functions. However, if such video signals having the pseudo-synchronization pulses stripped therefrom are to be output from the video system for a recording operation, the pseudo-synchronization pulses must first be re-inserted into the video signals so that any resultant copy is copy protected. Accordingly, it is often necessary for video systems to detect the presence of such pseudo-synchronization pulses in video signals.
In certain existing video systems, circuitry for detecting the presence of pseudo-synchronization pulses is included. In particular, certain video systems include video processing integrated circuits (“ICs”) having horizontal and vertical synchronization circuitry, such as horizontal phase locked loops (“HPLLs”), line counters, and vertical synchronization detectors. Such synchronization circuitry is included, for example, in the Phillips model SAF7113H video input processor IC. The synchronization circuitry included in this type of IC utilizes the horizontal and vertical synchronization signals included in a composite video signal. Accordingly, such circuitry makes the detection of pseudo-synchronization pulses a relatively simple matter since the horizontal and vertical synchronization signals provide stable reference timing points. However, when the detection of pseudo-synchronization pulses is required in a video system lacking the aforementioned type of synchronization circuitry, the cost of adding such circuitry can be prohibitive.
Accordingly, there is a need for a video system that avoids the aforementioned problems, and is therefore capable of detecting the presence of pseudo-synchronization pulses in video signals without requiring costly circuitry, or utilizing the horizontal and/or vertical synchronization signals included in a composite synchronization signal. The present invention addresses these and other issues.